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我很乐意向您寻求有关涉及光栅和矢量数据（由线表示）的缩放操作的代码的帮助。对不起，完整的代码稍长：

public class ZoomOperations extends JPanel {
  private java.awt.image.BufferedImage image = null;
  private Line2D.Double line = null;
  private double scale = 1.0, sx = 0.0, sy = 0.0;
  private int ratio = 20;
  private MouseManager manager = null;

  public ZoomOperations() throws IOException {
    line = new Line2D.Double();
    image = javax.imageio.ImageIO.read(new java.io.File("E:\\test.jpg"));
    manager = new MouseManager(this);
    addMouseListener(manager);
    addMouseMotionListener(manager);
    addMouseWheelListener(manager);
}

protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    AffineTransform trans = g2.getTransform();
    double x = 0.5*(getWidth() - scale * image.getWidth());
    double y = 0.5*(getHeight() - scale * image.getHeight());
    g2.translate(x, y); 
    g2.scale(scale, scale); 
    g2.drawImage(image, 0, 0, this);
    g2.setTransform(trans);                       //Incorrect line?
    g2.draw(line);
}

public void setPoints(Point start, Point end) { line.setLine(start, end); repaint();}
public void ZoomPlus() {scale = (++ratio + 2) / 10.0; repaint();}
public void ZoomMinus(){scale = (--ratio + 2) / 10.0; repaint();}

class MouseManager extends MouseAdapter {
    ZoomOperations item;
    Point start;

    public MouseManager(ZoomOperations item_){item = item_;}
    public void mousePressed(MouseEvent e){start = e.getPoint();}
    public void mouseDragged(MouseEvent e){Point end = e.getPoint();
        item.setPoints(start, end);
        item.repaint();
    }

    public void mouseWheelMoved(MouseWheelEvent e){
            int notches = e.getWheelRotation();
            if (notches < 0) ZoomPlus();
            else ZoomMinus();          
    }
}

public static void main(String[] args) throws IOException {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ZoomOperations zoom = new ZoomOperations();
    frame.add(zoom);
    frame.setSize(new Dimension(800, 600));
    frame.setVisible(true);
  }
}

不幸的是，缩放操作仅适用于栅格数据。矢量线保持其位置和大小。

没有缩放的初始图：

初始图

应用缩放加操作：

放大加

在我看来，以下行可能是不正确的

g2.setTransform(trans);

不涉及累积的移位 x、y 和比例......但是，错误可能在其他地方:-)

另一个问题：有没有更简单的方法在 Java 中实现缩放操作？非常感谢您的帮助...

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